This invention relates to storage racks and, more particularly, to high-rise storage racks, also known as Automatic Storage and Retrieval System racks (AS/RS racks). In the art, high-rise storage racks generally involve a structure of great height such as from 50-100 feet and comprise upright frame assemblies provided with suitable bracing and down-aisle tie means. High-rise racks also generally comprise a pallet support arrangement of the type used in "drive-in" and "drive-through" racks. These last-mentioned racks generally comprise two groups of upright frames placed one pallet apart with pallet load rail supports attached to the frames. The load rails upon which the pallets rest run from front to rear and support the pallets so as to enable the placing of pallets one in back of the other over the entire length of the load rails.
High-rise racks are also generally provided with a special automated storage and retrieval system which comprises mechanism for engaging the pallet on its underside for handling the same. These special systems generally comprise a so-called shuttle table which moves through the aisle and into a storage area from the aisle to engage the pallet on the bottom surface thereof. The shuttle table is usually 4-6 inches or more deep and places a load down on the rails. These rails leave the center area under the pallet free and clear for the movement of the shuttle table lifter.
Conventional high-rise racks use a series of down-aisle ties for innerconnecting and bracing both the front and rear columns of the upright frames at the same elevation. The front and rear columns are tied together at a plurality of levels in the rack structure in the longitudinal or down-aisle direction. These ties are then diagonally braced from the front end of the rack to the rear thereof and are diagonally braced to the floor in the rear plane. In the conventional practice of the prior art, it has been considered that this arrangement involving innerconnecting the front and rear columns of the frames by means of down-aisle ties is a most effective way of stabilizing the rack structure against down-aisle forces and to enhance the buckling resistance of the front columns.
On the other hand, there are serious disadvantages to the above-described bracing scheme. A major disadvantage is that the bracing arrangement of the prior art utilizes more space vertically than is necessary because of the nature of the handling equipment. The reason for this excess vertical space requirement is that there must be clearance above each stored load to the nearest obstruction to allow for the storage retrieval means to lift the load clear of the load supports prior to removing it from the rack. Typically, this clearance is about 3 or 4 inches above the top of each load. Also, under each load there must be room for the shuttle table of the automated storage and retrieval system to enter the rack structure sufficiently beneath the pallet so as to avoid contact with the pallet and also to subsequently raise and bring the pallet out of the rack structure. Typically, this clearance is about 7 to 9 inches. Because of the provisions of a down-aisle tie in the front end of the rack structure, the two clearances discussed above must be added together, and, in addition thereto, additional clearance must be allowed for the down-aisle tie member itself. On the other hand, the two clearances discussed above may be combined together (i.e., overlap) if there is no obstruction (such as a down-aisle tie) in the vicinity of the clearance window through which the storage retrieval system must operate. In a typical rack construction, the extra space required by reason of the use of a single down-aisle tie at a particular level may amount to as much as 6-8 inches of vertical clearance.
If a high-rise rack is to be installed inside a building that has a separate structural support system for the walls and roof, and therefore is limited to the available headroom, it is possible to use up one vertical load opening space just by the necessity of the extra down-aisle clearances of the prior designs. In a large system this can mean that as much as ten percent of the available volume for storage is lost because of the use of a down-aisle tie bracing system of the type used in the prior art. In the storage rack in accordance with the invention, the above-discussed problem of lost storage space is avoided by the use of a system of bracing the front column against the down-aisle forces and lateral column buckling without using a front end down-aisle tie member. This novel design eliminates the need for the extra clearances required and as discussed above, this novel bracing arrangement can substantially increase the storage capacity of any storage building. Moreover, this can be achieved without substantially increasing the steel required in the structure.
The columns in a high-rise storage rack generally represent fifty percent or more of the entire structure and those columns are directly proportional by weight and cost to the frequency from base to top with which they are tied. Lateral, or down-aisle, ties give lateral or down-aisle support to the columns. While more ties provide more support to the columns and reduce the cost, each down-aisle tie adds a minimum of 5 or 6 inches to the height of the rack or else reduces the number of units high within the fixed height available in the storage building as discussed above. By reason of the design in accordance with the present invention, lateral or down-aisle support for the column is added at every load level while at the same time leaving the entryway for the shuttle table under each load totally unobstructed. As an example, in the prior art conventional high-rise storage racks, there may be provided 11 loads high with 4 down-aisle ties under a 50 foot ceiling. By reason of the design in accordance with the invention it is possible to provide a twelfth load high under the same 50 foot ceiling by eliminating all the front down-aisle ties and supporting the columns down-aisle at 12 points instead of 4. Moreover, this provides a better and less costly storage system and because the columns are supported 12 times instead of 4 times, it is possible to save about one-third of the weight of the columns. Also, the adding of a twelfth-load high can increase the storage area nearly ten percent.
Briefly stated, the storage rack in accordance with the invention involves a system of bracing the front column against down-aisle forces and lateral buckling without using a front down-aisle tie member thereby eliminating the need for the extra clearances discussed above. The bracing scheme in accordance with the invention utilizes the load support arm rail sub-assembly with minor additions of cross or diagonal bracing within the sub-assembly to brace the front column from the back plane. Thus, the above-discussed advantages are achieved by the relatively simple expedient of changing the bearing rail assembly into a two-purpose bearing rail and brace frame assembly. Thus, the bearing arms and bearing rails are each doing double duty of both supporting the load to be stored and also resisting the down-aisle loads and forces that must be accommodated in every properly engineered rack structure.
The storage rack design in accordance with the invention has the additional benefit that it allows the front column of the frames to be braced in an economical manner at every level. This increases its strength substantially and, as an example, would permit, without significantly increasing the required amount of steel, increasing the capacity of a given column by as much as thirty-three percent over the conventional framing method.
A further advantage of the storage rack design in accordance with the invention is that it allows an easier erection procedure to be utilized. When the frames are erected, they are typically erected between a front and rear down-aisle tie protruding from the end of the already standing frames. This means that the frame being added must be threaded in between the front and rear down-aisle tie before it can be bolted in place. If there are no front down-aisle ties, it simplifies the erection in that the workmen will only have to match the frame with a rear down-aisle tie and have all the aisle clearance in front of the rack to work with in installing upright frames.
Another feature of the invention is that by eliminating the front down-aisle ties, more space is available for locating the sprinkler piping of a sprinkler system. In the prior art devices, there was often a conflict between the sprinkler piping and the front down-aisle ties and the horizontal cross braces.
Another advantage of the design in accordance with the invention results from the fact that the front down-aisle ties of conventional designs are normally constructed in front of the posts and become the first part of the rack encountered by a malfunctioning stacker and load means. By eliminating the front down-aisle tie assemblies, greater clearance can be provided to accommodate errant movement of the stacker and load means.